1. Field of the Invention
The present invention relates to a fluorescent body device, and more particularly to a fluorescent wheel with a fluorescent layer thereon which is rotated by a motor to emit selected fluorescence due to irradiation of exciting light of a predetermined wavelength, a light source device including the fluorescent wheel, and a projector which includes the light source device and which projects a color image onto a display screen.
2. Description of the Related Art
Recently, in various electronic devices, light sources are used which include a light emitting diode or a laser diode, or emits organic electro-luminescence or fluorescence. The light sources which emits fluorescence increases the density of energy of exciting light to be applied to the fluorescent substances included therein or increases the output of the exciting light to provide light of high luminance. These light sources are used in various fields, for example, of television or illumination applications. Various proposals are made for light sources using fluorescent luminescence in order to provide light of much higher luminance.
In order to increase the energy density or output of the exciting light, it is required to use an exciting light source which consumes a large quantity of electricity or a large-type exciting light source. Thus, these light sources are difficult to be used in electronic devices whose sizes have been reduced recently.
For example, JP H7-37511 proposes a face discharge matrix type plasma display panel where each of unit luminescence areas of the panel is increased by making rugged fluorescent layers covering the outer surfaces of adjacent isolation walls between which the unit luminescence area is defined, thereby increasing its whole luminescent area and luminance.
JP2005-277331 proposes a luminescent device that includes a light emitting device located at a center of a truncated conical recess in a reflector with a remaining space of its conical recess filled with an optically transparent substance containing dispersed fluorescent substances to increase the efficiency of luminescence from the fluorescent layer.
As described above, in order to obtain fluorescence of high luminance in the fluorescent light source, its luminescent area is increased or its fluorescence emitted in every directions is collected and used. However, in the above proposals, most of the fluorescence emitted in directions substantially parallel to the fluorescence emission surface of the fluorescent layer is useless and hence the use efficiency of the fluorescence is low.
Assume that a laser beam of high energy density is used as the exciting light source in a fluorescent wheel which has a reflective flat surface on which the fluorescent layer is provided to emit fluorescence when irradiated with exciting light. In this case, there is a high possibility that coherent light of high energy which has passed through the fluorescent layer and has been reflected by the reflective surface will be emitted as it is outward from the fluorescent wheel.
The present invention is directed to providing a fluorescent wheel of high use efficiency of fluorescence, a high safety light source capable of emitting light of high luminance, and a projector using such light source device.